The present invention relates generally to CAble TeleVision (CATV) data transmission systems, and more specifically to CATV data transmission systems that include high performance CATV diplexers and telephony modules.
CAble TeleVision (CATV) system networks have been widely deployed for distributing Radio Frequency (RF) television channels to homes of subscribers. More recently, CATV system networks have been employed in CATV data transmission systems for providing interactive data services to subscriber homes. A conventional CATV data transmission system includes a headend for receiving RF signals carried by a CATV network, a distribution system for receiving a broadband signal comprising the RF signals from the headend, and a plurality of subscriber drop cables for receiving respective portions of the broadband power from the distribution system. Each drop cable provides the broadband signal directly to subscriber equipment, which may comprise a suitable set top converter, a TV unit, or a Personal Computer (PC).
In a CATV data transmission system configured to provide interactive data services, a cable modem such as an Internet Protocol (IP) telephony based cable modem is typically disposed at a subscriber end of the CATV network. The cable modem typically comprises a CATV Input/Output (I/O) telephony module including an RF/telephony interface, which is configured to connect to the CATV network, receive data over the CATV network, and provide the received data to the subscriber equipment. In this way, the cable modem establishes a downstream data connection over a forward path from the CATV network to the subscriber. The RF/telephony interface is further configured to connect to the CATV network, receive data provided by the subscriber equipment, and transmit the received data over the CATV network. In this way, the cable modem establishes an upstream data connection over a return path from the subscriber to the CATV network.
The typical CATV I/O telephony module further includes at least one diplex filter (“diplexer”) configured to isolate the frequency of the downstream data from the frequency of the upstream data to assure that the downstream data signals and the upstream data signals do not interfere with each other. The diplexer generally includes a low pass filter section in the return path and a high pass filter section in the forward path, each of which may include one or more inductors such as a torroidal inductor.
One shortcoming of the typical CATV I/O telephony module is that the torroidal inductor(s) included in the diplexer is a relatively high cost component. For example, torroidal inductors are typically fabricated by manually wrapping wires around ferromagnetic cores. Although such a fabrication process can be used to make torroidal inductors with high Q values, the fabrication process is generally complicated and labor intensive and can lead to high manufacturing costs. Moreover, the high cost torroidal inductors can significantly increase the overall cost of the CATV I/O telephony module.
It would therefore be desirable to have a high performance CATV diplexer and telephony module that can be employed in CATV data transmission systems. Such a CATV diplexer and telephony module would be configured to achieve a high level of performance while having a low cost of manufacture.